A transfer supporter device, which is provided in an image forming device and includes a transfer supporter for transferring an image formed on an image supporter to a transported sheet or the transfer supporter itself, typically includes at least two roller members including a drive roller, and a transfer supporter, which is shaped like an endless belt, is stretched between the roller members, allowing the transfer supporter to rotate.
In this transfer supporter device, the drive roller causes the transfer supporter to rotate so that images which have been formed and sheets are transported. As continuously carrying out this operation, problems such as worn-down, fatigue and contamination of the transfer supporter occur so that the performance of the transfer supporter gradually deteriorates.
For this reason, generally the transfer supporter is replaced at predetermined intervals. Although the whole transfer supporter device may be replaced, only the transfer supporter is replaced in many cases. At any rate, to carry out the replacement, one has to draw out the transfer supporter from the inside of the image forming device, and after the replacement, put the supporter back to its original position.
Meanwhile, in an image forming device in which a sheet is provided on a transfer supporter and an image formed on an image supporter is transferred to the sheet, the sheet is supported by the image supporter and the transfer supporter so that the transfer is properly carried out.
Because of this arrangement, when the sheet is stopped on the transfer supporter due to reasons such as sheet jamming during the transportation due to some sort of trouble, the image transfer to the sheet is unlikely to be carried out properly, and hence the sheet on the transfer supporter has to be removed.
However, since it is difficult to remove the sheet when the same is held between the image supporter and the transfer supporter, it is necessary to release either one of the image supporter and the transfer supporter device from the other.
The distance between the released members cannot be long, in consideration of reasons such as the sizes of the image supporter, the transfer supporter, and the image forming device. Thus, the distance is restricted to be very short and hence one can hardly insert one's hand or finger to remove the sheet on the transfer supporter. For this reason, the sheet has typically been removed by drawing out a member, which is either one of the above-mentioned members and provided in the lower side of the image forming device, from the image forming device.
For instance, Japanese Laid-Open Patent Application No. 2-163238 (published on Jun. 22, 1990) discloses an image forming device arranged such that, a transfer supporter device is lowered and released from an image supporter by operating a handle, and then the transfer supporter and an up-and-down mechanism are drawn out altogether.
Also, Japanese Laid-Open Patent Application No. 6-316347 (published on Nov. 15, 1994; corresponding to Japanese Patent No. 2861721, registered on Dec. 11, 1998) discloses an image forming device in which a transfer supporter device is supported by a drawer and allowed to go up and down. In this image forming device, maintenances such as the removal of a jammed sheet, cleaning, and replacement of the transfer supporter device are performed by drawing out the transfer supporter device together with the drawer after causing the transfer supporter device to go down and separate from the image supporter.
Also, Japanese Laid-Open Patent Application No. 2002-214874 (published on Jul. 31, 2002; corresponding to US2002-98009 A1) discloses an image forming device in which, in sync with opening and shutting of outer coverings from a plurality of directions, a transfer belt is caused to separate from a photosensitive drum at the opened side. With this arrangement, one can carry out jam treatment from a suitable direction.
However, the arrangement in Japanese Laid-Open Patent Application No. 2-163238 has such a problem that, when performing jam treatment and maintenances, since the transfer supporter device is caused to go down for a long distance by operating an up-and-down mechanism such as a release lever, a large space and a lift mechanism are required below the image forming device.
According to the arrangement disclosed by Japanese Laid-Open Patent Application No. 6-316347, the image forming device is drawn out together with the drawer so that the volume of the members to be drawn out is significantly large. Further, in this arrangement, it is necessary to operate a member such as a large lever and this requires a large space inside the image forming device, thereby causing the image forming device to be large and heavy.
In the case of a tandem image forming device in which a plurality of image supporters are provided, the length of a transfer supporter device in the direction of the movement of a transfer supporter (i.e. in the direction orthogonal to the axes of roller members supporting the transfer supporter) is longer than the length of the transfer supporter device in the direction of drawing-out. On this account, the diameter of an opening through which a drawer supporting the transfer device has to be very long when the drawer is drawn out in the direction orthogonal to the direction of the movement of the transfer supporter of the transfer supporter device, and hence the strength of the frame of the image forming device tends to decrease from its drawing side.
The more the radius of the opening for replacing units regarding image forming and for maintenance is elongated, the more the strength of the frame of the image forming device decreases. In particular, when the direction of drawing out members such as a unit including the image supporter and a developing unit is identical with the direction of drawing out members for replacing the transfer supporter device and for maintenance, the radius of the opening has to be further elongated, and this causes significant decrease of the strength.
For this reason, it is necessary to provide a reinforcement or increase the thickness of members constituting a frame, resulting the upsizing and weight gain of the device.
According to Japanese Laid-Open Patent Application No. 2002-214874, since outer coverings can be opened and shut from a plurality of directions and a transfer belt is caused to separate from a photosensitive drum at the opened side, it is necessary to adopt a complicated arrangement, and a transfer supporting device including the transfer belt is not completely freed. Thus, it is, for instance, required to cause the transfer supporter device to be completely free when replacing the same.